I'm basing mine on 1080, and the fact that i remember reading that they have significantly streamlined the game, similar to Crysis and its sequel. 60fps might be stretch but it will be above 30 as long as he doesn't use 3D or goes heavy on anti-aliasing and whatnot but should be alright even maxed out, but you are probably right.

The system requirements did not increase all that significantly from the first one. Meh.

Can't really say because I don't know just how much rougher it is on systems than BL1, and optimizations matter, but if nothing else, you'll be able to play the game better than console users (it will look better, with higher framerate).

I think it's reasonable to expect you'll be able to get 30FPS at least on high settings, maybe even on the highest settings (with some drops).

Like I said though, we won't know for sure until the game is out.

There was a driver update for 500 series GPUs. Do you have This Update? It won't do much for you over previous updates (seems for Borderlands 2, it only affects SLI and 3D Vision aspects), but it'll include all previous updates (the one before that had a performance boost for BL2 I think).